It has long been known in the prior art to manufacture flexible tubing continuously of a wire helix covered by helically wrapped tape U.S. Pat. No. 2,486,387 is an early example of such apparatus wherein a grooved cantilevered mandrel turns against a similarly grooved press roller to draw the helically fabricated components together. In U.S. Pat. Nos. 2,539,853, 3,219,733 and 3,336,172, that general concept is also employed but with two or more outside guiding rollers acting upon the exterior of the helically fabricated tubing as it emerges continuously from the mandrel. In U.S. Pat. No. 2,539,853 the mandrel is made somewhat yielding by means of an inner rubber core.
It is the principal purpose of this invention to improve upon such prior art methods and machines so that the continuously helically fabricated product may be made at higher production speeds and with greater possible variations in the helix pitch, lead angle and diameter. These objects are accomplished by departing from the prior art concept of a relatively short grooved mandrel cooperating with a press roll of similar length. The helical components are drawn together in conventional apparatus of that type at a relatively confined longitudinal section of the product on the mandrel so that the wrapping forces are exerted on the tape and wire in a rather concentrated area. This can damage the components if production speeds are too high. In accordance with the present invention as set forth herein the wrapping forces are distributed evenly over a considerably larger longitudinal section of the product without the use of a press roller.